Automatic regulator for power-factor improving apparatus



April 22, 1930. v. F. SPlGAI 1,755,491

AUTOMATIC REGULATOR FOR POWER FACTOR IMPROVING APPARATUS Filed July 221924 '5 Sheets-Sheet 1 April 22, 1930. v, SPIGA] 1,755,491

AUTOMATIC REGULATOR FOR POWER FACTOR IMPROVING APPARATUS HUM-0 FiledJuly 22, 1924 3 Sheets-Sheet 2 April 22, 1930. v. F. SPIGAI 1,755,491

AUTOMATIC REGULATOR FOR POWER FACTOR IMPROVING APPARATUS Filed July 22,1924 5 Sheets-Sheet 3 III I Patented Apr. 22, 1930 PATENT OFFICE VINCENZO FAUSTO SPIGAI, OF LA SPEZIA, ITALY AUTOMATIC REGULATOR FORPOWER-FACTOR IMPROVING APPARATUS Application filed July 22, 1924, SerialNo. 727,584, and in Italy July 30, 1923.

The present invention has for its object an automatic regulator forapparatus intended to improve the power factor of electric distributionsystems. The devices intended torelieve the generators from theproduction of the magnetization component requisite for asynchronousmotors and to eX- clude this component from the long transmission linesand from the transforming stations may be divided into two broadclasses:

(a) The devices acting on the current before it enters the motorstators;

(b) The devices acting on the current after the motor stators.

The devices of the former class may provide the magnetization componentfor all asynchronous motors arranged after the point where the device isfitted on the line, no matter what the number of the motors may be. Thedevices of the latter class, at least as a rule, serve for one motoronly, however they may increase materially the motor power output. Thefirst class comprises: condensers, synchronous and self-synchronizingmotors; the second class comprise-s the Scherbius exciting machine andthe Kapp vibrator. In the case of the first class of devices it shouldalso be considered whether the synchronous motor will he used only as ameans for improving the power factor, or also for performing some otherduty.

The regulator according to the present invention may be used in order toregulate the excitation of a synchronous motor to maintain the powerfactor constant, whatever may be the variations in the circuit by whichthe motor is fed and in the load carried by the motor.

The regulator according to the invention is illustrated in theaccompanying drawings, wherein:

Fig. 1 shows the regulator in perspective View.

Fig. 2 shows the apparatus along with the regulation circuits.

Fig. 3 is a detail figure.

Figs. 4 and 5 are two diagrams illustrating the principle of themeasurement of the power and power factor in a triphase system.

1. Oar/rent circuits As the two current circuits, like theelectrodynamometers themselves are identical in construction andcapacity, what we are going to say about the current circuit of Happlies also to the current circuit of H As usual, on the metal base 1,which carries all the other parts, are secured the rear ends of thecylindrical guides 2 and 3, the front ends of which are connectedtogether by the plate 4. k

In the base 1 and plate 4 two holes are formed, in which is rotatablycarried the spindle 5 having at its forward end the knurled button 6.The spindle portion comprisedbetween the base 1 and the plate 4 isscrewthreaded, the thread being right-handed on one half and lefthandedon the other half of the said length. The metal supports 7, having asliding fit on the guides 2 and 3, are secured to the top face of theboxes 8 and 9 made of non-conducting material and containing the currentcoils 10 and 11. Secured in the center of the metal boxes 8 and 9 aretwo cylindrical internally tapped bushes forming two nuts engagedrespectively by the right-hand, and the left-hand thread of spindle 5.The ends of the winding of the current coils 10 and 11 are connectedthrough copper strips 12 to the supports 7; while the coils aretravelling along the spindle 5, the

supports 7 are kept in contact with the guides 2 and 3 by the platesprings 18 secured to the said supports. Then by means of the knurledbutton 6 the spindle 5 is revolved, the current coils 10 and 11 travelin opposite directions, their inner faces moving away from or nearer toeach other, the pressure coil 14 being movably arranged between the two;the distance between the inner faces of 10 and 11 is indicated at anymoment by the pointer fixed to the spindle of the gear wheel 15, thisgear being actuated by the pinion l6 keyed on the spindle 5. The guides2 and 3, the detail of which is shown in Fig. 3, consist each of twoequal lengths of metal rod, the two halves in each guide being insulatedfrom one another, from the base 1 and from the plate 4. a

2. Tensionv circuits Into the metal supports 17 and 18 secured to thebase 1 are screwed two adjustable screws fitted with agate, on whichrest the hardened steel ends of the rotatable spindle 19 of the movableequipment. The tension coils 14 and 14 are carried by the metal rod 20having midway of its length an. enlargement secured to the spindle 19 bymeans of a set-screw. The springs 21 and 22, threaded on the spindle 19and acting in opposite direction to each other, serve to position themovable equipment to zero, and the small lever arm 23, likewise carriedby the spindle 19, serves to transmit the movements of the movableequipment to the swinging rod 24 of the relay.

3. Uontrolling relay To the upper support 17 is fixed the small metalframe 25, in the top and bottom of which are provided two adjustablescrews fitted with agate and carrying the rotatable spindle for theswinging rod 24. The frame 25 has two movable arms for attachment of twosprings tending to bring the rod 24 back to zero. On the swinging. rod24 are provided: a pin whose steel pointed ends rest on agate, aplatinumplate 26 adapted to make contact with one or the other of theplatinum cylinders carried by the screws 27 and 28. fitted in'thebrackets 29 and 30 provided on the rod 31; this rod being identical inconstruction to the. guide rods 2 and 3 (Fig.

The diagram of Fig. 2 shows the regulator as fitted on the main bus-barsof a distributing central station provided with a thermal reserve plantand fedv from a generating central station, the distributing stationbeing equipped with a synchronous motor for the purpose of increasingthe power factor.

In the direct current circuit R a graduated rheostat c is inserted, therheostat being operated by hand through the handwheel d or by the smallrotary converter e which in its turn is automatically controlled by theregulator. The extension of the converter spindle is provided with a,worm f meshing with the helical wheels g and h. The converter'e runs atconstant speed and always in the same direction and drives the helicalwheels g and h, which run loose as long as no current circulates throughthe coils -e' and 7c of the electro-magnetic clutches; when either ofthe said coils is traversed by the current, the helical wheelsalternatively drive the gear wheels Z- and m. The revolving direction of-Z and m indicated by the arrows is transmitted to the gear wheel ncarried by one end of the spindle -p-, while the other end of p carriesthe movable contact 0 and the hand-wheel cl of the rheostat. Theconverter c-, besides supplying the necessary power for operatingthemovable contact 0 of the rheostat, converts the current fromalternating into direct current, as required for coils of theelectromagnetic clutches and of the relays.

In the direct current circuit of the converter c, which supplies theoperating currents for the relay, are arranged the two noload circuitbreakers 5O and51, controlled respectively by solenoids 52 and 53energized from the transformers 54 and 55 in the supply leads of thesynchronous motor so that when this motor is not running this directcurrent circuit is opened. It will also be opened upon failure of anyone phase of the motor.

Referring to Figs. 4 and 5, the measurement of the power andpower factorof a triphase system is efiected, as well known, in the followingmanner:

The instantaneous power Pi of a starconnected triphase system is given(Fig. 4) by Pi= c +i e +i c wherein i i i are the line currents and e e6 the star voltages of the system. As i =i +i the equation becomes: Pi=i(e e +i (e e The average power is given by:

and is measured by the readings of two wattmeters. If we indicate by WVthe two wattmeters and by a (t the respective readings, we have: a +a=Pm. The value of the power factor is given by (t -H1 cos p 1 3 M r 2 Ifthe circuit in question is a high tension circuit, current and Voltagetransformers TL T1 and TE TE (Fig. 2) should be used.

In Fig. 5 the currents and voltages at play are represented by vectors,E E E being the star voltage and I 1 I the currents in each of the threewires. The current coil of W will be traversed by a current proportionalto L and in phase with the latter, while the corresponding tension coilwill be traversed by a voltage proportional to E and in phase with thelatter. The power indicated by W is directly proportional to E cos IE iE cos (30 0). At the same moment the power indicated by will anced, wemay write E E =E =E, I =I =I I, (p (p (p and accordingly E 3=E 3=E =E 3.'Ihe power indicated by W is then proport1onal to 1/IE[cos (30 a)+OS(300)] 3IEcos a. If we replace the expressions wattmeters, indications andpower by the expressions electrodynamometers, component motive couplesand resulting motive couple, we have 1. Component motive couple of H O=IE R cos (30 (I) 2. Component motive couple of H 0 =IE /5 cos (II) 3.Resulting or total motive couple:

0 4543 [cos( +003 (30+ p)], that is to say 0 31]? cos (p (III) whichtends to produce the deviation of the movable equipment of theregulator.

The regulation effected by the regulator is based on the variations ofthe angle (p as re sulting at the main bus-bars of the distributingcentral station due to frequence and pressure variations occurring atthe generating central station, to ohmic and inductive drop in the line,and to variations in the Working conditions of the users plants lyingalter the bus-bars of the distributing central station. In order tomaintain a constant value of the angle at the bus-bars of thedistributing station, it would be necessary that for each of the saidvariations a corresponding regulation should be made in the excitingcurrent of the revolving inductor field R of the synchronous motor. Itsuffices to consider the quickness and simultaneousness with which thevariations of the angle (,0 may take place to realize the utterimpossibility for an industrial plant to adjust the value of theexcitation by the mere operation. of the rheostat c by hand in spite ofthe attendants greatest experience and good will.

For the purpose in view it will suflice to demonstrate that theoperation of the rheostat and the adjustment of the excitation valuetowards maintaining a steady angle (p at the bus-bars are obtainedreadily and with certainty by means of the automatic regulation carriedout by the regulator. It is well known that, by suitably adjusting theexcitation currentofthe revolving inductor field in the running motor,the load on the bus-bars at the generating station can be considered inrespect to the impressed voltage under three diliterent conditions, viz.

.1. As an ohmic load, when the currents at the bus-bars are in phaserelatively to the impressed voltage; the angle (p is 0 and the vectors II 1,, representing the currents at the'bars, coincide with the vectors EE E representing the impressed voltage V (Fig. 7).

2. As an inductive load, when the currents lag behind the voltages, theangle 0 increases and the vectors I I I lag behind the vectors E E E(Fig. 6).

8. Asa capacity load,when the currents lead relatively to the voltagesthe angle (,0 increasing and the vectors I I I lea-d relatively to thevectors E E E (Fig. 5).

Let us assume that in connection with the h conditions 2 and 3 the anglebe for instance -26 lag, and =26 lead respectively. If in the formulae Iand II We substitute the values: 0 0", =26 lag, =26 lead, we obtain:

For condition 1:

0 =lE cos (30 -0 =1EJ3 086603 0 =IEJ cos (30+0) =IEJ3 036603 The IIIformula becomes:

0 =1EJ3 (0.99750) 0 =lE (0.64279) 0r=]E (-0.35471) And for condition 3:

, 0 =IE (0.64279) 0 =IE (0.99750) 0=IEJ3 (0.35471). When for condition 1(angle =O) the component couples C and C are equal in value and oppositein direction, the total couple C? 1s zero and the movable equipment,

being'subjected only to the action of the antagonistic springs, remainsat rest (pointer at zero).

When, on the contrary, with condition 2 the angle 0 26 lag, thecomponent couple C increases and C decreases in value, the

total couples is Or=IE /(0.35271), the movable equipment revolves in thesense of bringing the platinum plate 26 (Fig. 2) into contact with thescrew 27.

When finally condition 3, obtains, the angle (,0 being 26 lead, thecomponent C will decrease and the component C will increase in value andthe total couple is accordingly proportional to 0r=IE /3(0.354=71). Themovable equipment then turns in such a direction as to bring theplatinum plate 26 into contact with the screw 28.

Let us now examine how the regulation practically is effected whencondition 1 obtains.

The attendant operates the hand-wheel c of the rheostat (Z by hand (Fig.2) and therewith adjusts the value of the excitation until he obtainscos 0 1 at the bus bars, this angle being read on the scale which weassume to be fitted up at the bus-bars. If after the said operation weobserve the regulator, we shall see that the movable equipment is atrest position and maintains the plate 26 insulated from both screws 27and 28. If the condition 2 sets in, the movable equipment will bedisplaced and the direction of the displacement will be to the effect ofbringing the plate 26 into contact with the screw 27 The movable arm ofthe rheostat 0, as set out above, is shifted to the effect of loweringthe resistance of the inductor field R and thus raising the value of theexcitation until the movable equipment is I restored to its restposition.

If, instead, condition 3 sets in, the movable equipment turns in thesense of bringing the plate 26 into contact with the screw 28. Therheostat arm 0- is then shifted to the elfect of increasing theresistance inserted in the circuit of the inductor field R and thuslowering the excitation until the movable equipment returns to its restposition.

A. regulator whose automatic regulation should be confined to maintaincos =1 would find no practical application because,

., as well known, the total power factor of the very best plants, underthe most favorable conditions, hardly reaches 0.8.

lVith reference to condition 2, let us suppose that the automaticregulation of the rheostat chas been temporarily eliminated by shutting"off the current from the relay coils r and sor' from the coils -iand 7cof the electromagnetic clutches. By adjusting the excitation currentthrough the handwheel rc let now the power factor at the bus-bars bereduced from cos =1 to cos =O.9 lag; the angle corresponding to cos(p=0.9 is 26. By substitut ing this value in the Formulae I and II Wehave: 0 =IE /(0.98750), O =IE J3 (0.64279) and the Formula III becomes,

'0 =lE /3(O.35771). The movable equipment will be shifted from the restposition and maintain the plate 26 in contact with the screw 27. r

If no cause intervenes to modify the frequency and pressure at thebus-bars in the distributing station nor the load, the movable equipmentwill steadily remain in the new position since the automatic regulationthrough the rheostat c is disconnected.

If it be wished to restore the movable equipment to its rest positionand to maintain (p =26 at the bus-bars the component couples C and Cshould be rendered equal in value and opposite in direction, that is tosay the total couple C2 should be nullified.

It now remains to consider how this object can be realized withoutaltering the electric characteristics of the two electrodynamornetersand without making any alterations in the excitation, frequency, tensionand load.

It has already been stated that the component couples C and C areproportional to the main currents circulating through the current coilsand to the shunted currents circulating through the pressure coils. Ithas also been demonstrated that when the current tension and angles arethe same in the different phases and the main currents are in phase withthe shunted currents, the couples C and C2 are equal in value andopposite in direction and the total couple is 07 0. We now must addthatall these conditions are required but not sutficient to enable to saythat the two couples C and C are equal and that the total couple isnought.

In fact if we gradually move the current coils 10 and 11 up to aninfinite distance apart from the pressure coil 14 of H the componentcouple C will gradually sink in value till it is nullified.

The regulation effected by the regulator throughout the series of thesuccessive Values of angle (p comprised between and -6() is based on therelative distance of current coils from the pressure coils in the twoelectrodynamometers. Practically the operation for varying the saiddistance is efiected by means of the knurled buttons 6 and 6 (Fig. 1) byturning the knurled button 6 clockwise the current coils 10 and 11 aremoved away from the pressure coil 14 and the movable equipment isrestored into its rest position.

IVhen closing the circuit of the relay coils 9" and s or that of thecoils 1I- and k of the electromagnetic clutches, the movable contact -0of the rheostat c remains at rest in the position in which it findsitself. If the button is turned further on and the current coils arethus removed farther away from the pressure coil, the movableequipmentturns and operates the movable contact 0 of the rheostat c to the effectof further lowering the value of the excitation by increasingthe angle(p at the bus-bars.

An anticlockwise operation of the knurled button moves the current coilsnearer to the pressure coil and causes the movable equipment to bedisplaced in opposite direction to the foregoing one, therewith turningthe movable contact 0- to the effect of increasing the excitation andlowering the value of the angle (p so as to restore cos p=1.

The regulation for condition 3 is obtained by turning the knurled button6 thereby moving the current coils 10 and 11 away from or nearer to thepressure coil 14 in H 28nd thus varying the intensity of the coupleHaving now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is 1. An apparatus for the regulation of the power factorin a polyphase net, comprising a pair of contacts, a movable contactmeans for making contact with one or the other of said first mentionedcontacts, means for actuating said movable contact, comprising anelectrodynamometer, said electrodynamometer comprising a pair of movableour- 1 rent coils, and a movable voltage coil, means or controlling thetorque on said voltage coil, means for transmittingthe movement of saidvoltage coil to said movable contact means.

2. In an apparatus for the regulation of a power factor in a net,comprising a pair of contacts, movable contact means for making contactwith one or the other of said first mentioned contacts, means foractuating said movable contact means, comprising a pair ofelectrodynamometers, each of said electrodynamometers comprising a pairof current coils and a movable voltage coil, means for varying theposition of the current coils of each dynamometer with respect to thevoltage coil of said each electrodynamometer, and means for transmittingthe motion of said voltage coils to said movable contact means.

3. An apparatus for the regulation of the 7 power factor in a polyphasenet system, comprising a pair of contacts, movable contact means formaking contact with one or the other of said first mentioned contacts,means for actuating said movable contact, comprising anelectrodynamometer having a pair of movable current coils, and a movablevoltage coil, means for varying the position of said current coilsrelative to said volta e coil for controlling the torque of said vo tagecoil, and means for transmitting the movement of the voltage coil to themovable contact means. 7

VINCENZO FAUSTO SPIGAI.

